ASSOCIATED PRESS WRITER

DIANE DUSTON

WASHINGTON (AP)—More than 100 angry teen-agers descended upon a California cable TV company after it decided to drop MTV in favor of a small broadcast station it is required to carry under a new federal law.

The students in Marin County picketed Chambers Cable for several days in May until they got a promise that MTV would be spared.

Cable subscribers across the country have seen programming changed to conform to the ‘‘must carry’‘ provision of a cable law passed by Congress last year. On Tuesday, the Supreme Court said it would review whether the provision is constitutional.

The law requires cable companies to reserve at least one-third of their channels for local TV stations and public broadcasting.

In many of the nation’s 11,000 cable operations that has meant dropping a cable network or two. Most of the changes occurred during spring and early summer as a cable industry lawsuit against the provision worked its way through the courts.

‘‘There wasn’t a whole lot of shakeup,’‘ said Brad Stillman of the Consumer Federation of America. He said the law is meant to protect free, over-the-air television, and 40 percent of households with television still don’t have cable.

Lawmakers feared that unless local broadcasters have guaranteed access to cable systems, they might be squeezed out of existence as cable stations take an increasing share of advertising dollars.

But cable companies complained they were being forced to drop more popular cable networks for small, specialized broadcast stations. In the Marin County case, Chambers Cable had to find room for Spanish language and Asian stations they had not been carrying.

The Supreme Court says it will hear cable companies’ arguments that forcing them to carry those stations violates their free-speech rights under the First Amendment.

A three-judge federal panel in the District of Columbia ruled 2-1 against the cable industry’s challenge in April, saying Congress is regulating a commercial commodity, not speech. The law is aimed at guaranteeing fair trade and any effect on speech is ‘‘simply a byproduct,’‘ the judges said.

In the appeal, the cable companies argued that forcing them to carry certain television stations would be like requiring newspapers to publish articles by certain writers.

The requirement is part of the Cable Television Consumer Protection and Competition Act, which is having trouble on another front as well.

Congress intended that the law restrain cable rates, and it is causing rates to go down in many places, but so many complaints have be received by lawmakers about increases that the Federal Communications Commission may have to change its rate structure.

‘‘I am very puzzled by the explanations being offered by cable operators for the large numbers of rate increases,’‘ Rep. Edward Markey, D-Mass., said at a hearing Tuesday of his House Energy and Commerce telecommunications subcommittee.

He told the three FCC commissioners assembled for the hearing that they must stop the industry from raising rates that aren’t justified.

FCC Chairman James Quello said a survey of the nation’s top 25 cable companies would be completed soon.

He said he wanted to be sure any corrective action by the FCC is based on ‘‘factual evidence rather than anecdotal press accounts or local rate complaints by what would probably turn out to be a minority of national cable subscribers.’‘